With the increased need and demand for securing exterior doors against unauthorized and forcible entry, there has been a steady development of improved security locks. Such improvements have been directed to pick resistant cylinders, longer and stronger dead bolts, and guard plates to prevent removal of lock cylinders. However, no matter how secure the lock cylinder and bolt are, the fact remains that the bolt generally extends only about one inch into an aperture in the door jamb after passing through a small strike plate mounted on the jamb. The strike plate is usually secured to the jamb by a pair of screws that extend a small distance into the jamb. Moreover, the location of the strike plate and the aperture into which the lock bolt extends is close to the inner edge of the jamb with a relatively thin section of the jamb retaining the bolt against inward movement. Thus, in many instances, a person may cause the bolt to rip through the retaining section of the jamb simply by throwing his weight against the door. In this way entry may be gained without disturbing or overcoming the security offered by the lock itself. Efforts have been made to strengthen strike plates. See, for example, U.S. Pat. Nos. 4,005,890 and 4,186,954.
Also, since the dead bolt generally extends only about an inch into the door jamb, and the jamb often is only a framing member spaced from the two by four's that form the basic wall structure, the door jamb can be sprung with a crowbar and pried away from the extended bolt. It is even known that hydraulic jacks have been used to spread the door jambs to disengage the jamb and strike plate from the extended dead bolt. The same techniques can be used to free the door at its hinge side since the hinges are secured near the inner edge of the door jamb by relative short screws.